docs: def delete_existing_cname(env, zone_id, dns_name):
      """Delete an existing CNAME record.
  
      This is used when updating to multi-region for deleting old records. The
      record can not just be upserted since it changes types.
  
      Args:
          env (str): Deployment environment.
          zone_id (str): Route53 zone id.
          dns_name (str): FQDN of application's dns entry to add/update.
      """
      client = boto3.Session(profile_name=env).client('route53')
      startrecord = None
      newrecord_name = dns_name
      startrecord = find_existing_record(env, zone_id, newrecord_name, check_key='Type', check_value='CNAME')
      if startrecord:
          LOG.info("Deleting old record: %s", newrecord_name)
          _response = client.change_resource_record_sets(
              HostedZoneId=zone_id, ChangeBatch={'Changes': [{
                  'Action': 'DELETE',
                  'ResourceRecordSet': startrecord
              }]})
          LOG.debug('Response from deleting %s: %s', dns_name, _response)